Polarimetric detection of non-radial oscillation modes in the β Cephei star β Crucis
Abstract :
Here we report the detection of polarization variations due to non-radial modes in the β Cephei star β Crucis. In so doing we confirm 40-year-old predictions of pulsation-induced polarization variability and its utility in asteroseismology for mode identification. In an approach suited to other β Cephei stars, we combine polarimetry with space-based photometry and archival spectroscopy to identify the dominant non-radial mode in polarimetry, f2, as mode degree ℓ = 3, azimuthal order m = −3 (in the m-convention of Dziembowski) and determine the stellar axis position angle as 25 (or 205) ± 8°. The rotation axis inclination to the line of sight was derived as ~46° from combined polarimetry and spectroscopy, facilitating identification of additional modes and allowing for asteroseismic modelling. This reveals a star of 14.5 ± 0.5 M⊙ and a convective core containing ~28% of its mass—making β Crucis the most massive star with an asteroseismic age.
Publication : Nature Astronomy, Volume 6, p. 154-164
DOI : 10.1038/s41550-021-01531-9
Bibcode : 2022NatAs...6..154C